Split screen in Actionscript 3 - actionscript-3

Question

I'm trying to make a pure AS3 game, and need a way to split the screen so that two players can have individual "cameras" that follow the around the game world. The problem is that a sprite can't have multiple parents. I'm trying to hack my way around this problem by having classes that duplicate sprites and manage all of their updates, but I'm not getting very far and my code is getting very, very ugly.
Does anyone know a good workaround or method for doing this? I can't seem to find much on-line on the subject.

Answer 1

I think you should use BitmapData copyPixels method
.copyPixels(point_0, rectangle_0)---> FirstPlayerScreen
World.Bitmap -
.copyPixels(point_0, rectangle_0)---> SecondPlayerScreen

Answer 2

Thanks for everyone's suggestions. What I've ended up with is a World class that I can add regular Sprite objects to as children. The World object manages and updates copies of those sprites, and world.getCamera() can be called as many times as necessary to display custom copies of the game world.
The key part is making copies of the sprites, this is the function I wrote to do that:
public function bitmapCopy(original:DisplayObject):Sprite
{
var returnSprite:Sprite = new Sprite();
if (original.width == 0 || original.height == 0) return returnSprite
var x = original.x; var y = original.y
var rotation = original.rotation
original.x = 0; original.y = 0; original.rotation = 0
var bounds:Rectangle = original.getBounds(original.parent)
var m:Matrix = new Matrix()
m.tx = -bounds.x
m.ty = -bounds.y
var bitmapData:BitmapData = new BitmapData( bounds.width, bounds.height, true,
0xFF0000 );
bitmapData.draw(original, m);
var bitmap:Bitmap = new Bitmap( bitmapData );
bitmap.x = bounds.x
bitmap.y = bounds.y
returnSprite.addChild(bitmap);
returnSprite.x = original.x = position.x
returnSprite.y = original.y = position.y
returnSprite.rotation = original.rotation = rotation
return returnSprite;
}
The returned Sprite can be added to the stage and will act in exactly the same way as the original (except for being static, of course). Hopefully this should help anyone else who comes across this problem.

Answer 3

Your theory is on the right track - you're probably just stumbling over your implementation. Organization and keeping things object-oriented will be your best friend in this scenario.
It's hard to give you a good example based off of a limited description of your game, but in general, I'd have a Screen class that can be instantiated multiple times, and I'd keep track of each instantiation (that gives us our multiple "players"). Each Screen has a stage, and you're building your game world on that stage.
The key here is data organization and good communication. Remember, there's only one "world", and you're just showing multiple instances of it. So you'll want a central Model to store data about every object in your singular game world. That Model will drive the rendering of that world to your multiple screens. If a player changes an object on their screen (let's say they move it), then you'll update the Model with that object's new location. Then, you'll broadcast those new coordinates to each Screen instance, so that all of your screens will update.
How you "broadcast" this can vary (and depends largely on the real-time nature of your game). If your game is very real-time and you're running a game loop, then you may just want to pass the objects' data along in every loop, and they'd update that way. If your game isn't as dependent of being real-time, then you can set up event listeners or a custom notification system that'll alert all of the instances of an object to update itself.
I know this is very high-level, but it's hard to give an in-depth answer without more info about your game. Hopefully this helps point you in the right direction - what you're attempting is definitely not simple, so don't get discouraged!

Answer 4

If you develop your game using MVC architecture principles then it should be trivial to draw your game twice, each player having an instance of the game's "view" but positioned according to a different character. If you give a layer mask to each instance then you could put the two instances side by side and so create a split screen effect.
Happy coding!

Answer 5

I'm working on a split screen myself just now:
masking to draw 1 world in 2 branches of your DisplayObject tree (separated cleanly), copying pixels for a split screen is a bad idea
data object to describe the world (not Sprite or DisplayObject)
Works very well so far. I've got 1 level, 2 players who move independently from each other and 2 screens that follow one player at a time. I see the other player in one player's screen and the one player in the other player's screen.
Here is how I did the data object part:
Define a central data object which describes the world and all it's world objects.
Write: make some sprites being able to manipulate 1 object of the world.
Read: update sprites by checking the properties of the world objects. 2 Screens -> 2 sprites for every world object. Check them every frame or try events.